Théodore Rousseau, in full Pierre-étienne-Théodore Rousseau (born April 15, 1812, Paris, France—died December 22, 1867, Barbizon), French painter who was a leader of the Barbizon school of landscape painters. His direct observation of nature made him an important figure in the development of landscape painting.

Rousseau, the son of a tailor, began to paint at age 14. In the 1820s he began to paint out-of-doors directly from nature, a novel procedure at that time. Although his teachers were in the Neoclassical tradition, Rousseau based his style on extensive study of the 17th-century Dutch landscape painters and the work of such English contemporaries as Richard Parkes Bonington and John Constable. His early landscapes portray nature as a wild and undisciplined force and gained the admiration of many of France’s leading Romantic painters and writers.

In 1831 Rousseau began to exhibit regularly at the French Salon. But in 1836 his Descent of the Cattle (c. 1834) was rejected by the jury, as were all his entries during the next seven years. Despite the Salon’s censure, his reputation continued to grow.

Rousseau first visited the Fontainebleau area in 1833 and, in the following decade, finally settled in the village of Barbizon, where he worked with a group of landscape painters, including Jean-Fran?ois Millet, Jules Dupré, Narcisse-Virgile Diaz de La Pe?a, and Charles-Fran?ois Daubigny. Their artistic goals were similar, and they became known collectively as the Barbizon school. During this period Rousseau produced such tranquil pastorals as Under the Birches, Evening (1842–44), reflecting the influence of Constable.

After the Revolution of 1848, the Salon briefly relaxed its standards, and Rousseau finally received official recognition as a major figure in French landscape painting. His works were well represented in the Universal Exposition of 1855, and he became president of the fine-arts jury for the Universal Exposition of 1867. Rousseau’s paintings represent in part a reaction against the calmly idealized landscapes of Neoclassicism. His small, highly textured brushstrokes presaged those of theImpressionists.